LEDs (light emitting diodes) have low power consumption, high efficiency, quick reaction time, long lifetime, and the absence of toxic elements such as mercury during manufacturing. Due to those advantages, traditional light sources are gradually replaced by LEDs.
A conventional illumination module includes a substrate, an LED package arranged on the substrate, and a light diffusion plate located at a light path of the LED package. Light emitted by the LED package enters the light diffusion plate via an incident surface of the light diffusion plate and thereby radiates out of the light diffusion plate. However, the light entering the light diffusion plate is easily distributed uneven, which leads to a light brightness of the light diffusion plate gradually decreasing along a direction away from the light package. Such that, a brightness of the illumination module will be not uniform.